A wide cross in "Liliaceae"

Michael Mace michaelcmace@gmail.com
Mon, 25 Jun 2012 11:05:39 PDT
Thanks everyone for this very interesting thread.

To add a bit to the discussion on chromosome numbers, my amateur experience
so far has been that the "rules" apply very thoroughly until they don't, and
you cannot know where the boundaries are until you test them.

Case in point, in the work I've been doing with Moraeas, most of the species
I am crossing (M. aristata, gigandra, neopavonia, etc) all have the same
chromosome number, 2n=12.  However, some are 2n=24 (M. villosa,
tulbaghensis).  In other words they have double the number of chromosomes.

Here's what is supposed to happen:

--Crosses between the 12-chromosome species should have a good chance of
being fertile.

--Crosses between the 24-chromosome species should have a good chance of
being fertile.

--Crosses between the 12- and 24- chromosome species should produce
"triploids" that may be vigorous but are almost always infertile, because
they do not inherit a matched set of chromosomes.

So what happens in real life?

--Many of the crosses that are 12 x 12 produce plants with withered anthers,
little or no pollen, and sometimes won't even set seed if pollinated from
something else.  That makes them a dead end for breeding.
--Many of the 12 x 24 crosses produce plants with abundant pollen, and they
set seed readily.

One more data point: a famous cross in Moraea history was speciosa x
polystachya, which is 20 x 12.  It was important because M. speciosa does
not look like a traditional Moraea at all.

I wish I had the capability to do a chromosome count on these things myself.
In the absence of that, my philosophy is to cross everything and see what

Comments/suggestions from the more experienced and educated people on the
list would be deeply appreciated.

San Jose, CA

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